My Dad, now passed, flew the F-86 for the Michigan National Guard (171st). In 1954 he said they were red lighted and took off to intercept something that buzzed a airliner. They had no radar contact, so they went to the path of the airliner.

He said they were at around 30,000 feet and when something went past them at a insurmountable speed and almost lost control of his plane. He then went into a high 180 turn to try and pursue it, but never made contact with the craft. He said he had been buzzed in training by other aircraft going in opposite directions, but he said this thing was going thousands of MPH. He said whatever it was it wasn't American made.

He said he never put it in a written report, but communicated it with his base as it was happening & after being debriefed.

I'm sure there's many more untold encounters out there.